This story is insanely captivating. Tho i must say. And this isn't a criticism of the storyline just a personal pov from someone thats been in an abusive relationship.
Spoiler below! If you haven't read the demo yet!
If romancing Zero means the poly route is with Vincent. I decline. Zero seems like a really broken soft person and i think everyone will want to protect him and gravitate towards him especially because of the connection he has with MC (which is crazy btw) but Vincent seems volatile, his comments about torture, his leering at MC and his behavior seems borderline abusive. I don't think I could romance someone who would still technically also be in a relationship with someone who seems abusive towards them. If it was anyone else that still liked Zero and treated them well even if themselves and our MC have no romantic relationship at all I'd feel less... iffy about it. Much rather romance a literal alien that could've probably killed my MCs mother than put myself through that trauma.